Wet processing is used extensively during the manufacture of integrated circuits, which typically comprise electronic component precursors such as semiconductor wafers or flat panels. Generally, the electronic component precursors are placed in a bath or a vessel and then contacted with a series of reactive chemical process liquids and rinsing liquids. The process liquids may be used, without limitation, for etching, photoresist stripping, prediffusion cleaning, and other cleaning steps of the electronic component precursors. See, e.g., U.S. Pat. Nos. 4,577,650; 4,740,249; 4,738,272; 4,856,544; 4,633,893; 4,778,532; 4,917,123; and EPO 0 233 184, assigned to a common assignee, and Burkman et al., Wet Chemical Process-Aqueous Cleaning Processes, pp.111-151, in Handbook of Semiconductor Wafer Cleaning Technology (edited by Werner Kern, Published by Noyes Publication Parkridge, N.J. 1993), the disclosures of which are herein incorporated by reference in their entirety.
In a typical wet processing technique, the electronic component precursors are treated in either a full flow vessel (a vessel closed to the environment), single tank, compact wet bench, traditional wet bench, or bath. In typical wet processing techniques, the electronic component precursors are exposed to reactive chemical process liquids to either remove (i.e., clean) contamination on the electronic component precursors or to etch some part of the surface. After this cleaning or etching is performed, the chemicals will adhere to the surface or surfaces of the electronic component precursors. The adhered chemicals generally may be removed before treating the electronic component precursors with the next reactive chemical process liquid so that the chemical residue does not contaminate the next reactive chemical process. Traditionally, the adhered chemical is removed by rinsing with deionized (DI) water.
After the chemical treatment steps are completed, the wafers are generally dried. Drying of the electronic component precursors can be done using various methods, with the goal being to ensure that there is no contamination created during the drying process. Methods of drying include evaporation, centrifugal force in a spin-dryer, steam or chemical drying of wafers, including the method and apparatus disclosed in, for example, U.S. Pat. Nos. 4,778,532 and 4,911,761.
One of the most important considerations for an effective wet processing method is that the wafers produced by the process be ultraclean (i.e., with minimum particle contamination and minimum chemical residue). Certain techniques use DI water to remove particulate matter and chemical residue after each chemical treatment step.
Traditionally, the electronic component precursors are transferred from a reaction chamber containing the chemicals to a rinsing tank containing DI water. Alternatively, the electronic component precursors can be left in the reaction chamber containing the chemicals and the chemicals can be displaced from the reaction chamber by introducing DI water into the chamber. The DI water can be introduced into the reaction chamber either from the top or bottom of the reaction chamber. See, e.g., U.S. Pat. Nos. 4,778,532 and 4,984,597, the disclosures of which are herein incorporated by reference in their entirety. In such a reaction chamber where the electronic component precursors are stationary and where chemicals are displaced by DI water, usually water is introduced from the bottom of the tank, and the chemicals are drained from the top of the tank. It is also possible, however, to introduce water into the top of the tank and to drain the chemicals from the bottom of the tank.
Traditionally, the chemicals in the reaction chamber and the displacing DI water also have the same temperature, which usually causes intimate mixing of the chemicals and the DI water. This causes the chemicals to be continuously diluted with water, which is undesirable since it is both environmentally preferable and cost effective to recycle the chemical solutions. In addition, it takes significantly longer to rinse when mixing occurs than if no mixing occurs. If minimal mixing occurs, the chemical solution is quickly removed from the vessel, as in plug-flow techniques. If mixing continuously occurs, however, then rinsing takes much longer, and theoretically approaches the model of a CSTR (continuously stirred tank reactor). Verhaverbeke, S., McConnell, C., Parker, J. W., and Bay, S., Scientific Rinsing and Drying on Macro and Microscale (SPWCC, Mar. 4-7, 1996) in Semiconductor Pure Water and Chemicals Conference 1996 (Balazs Analytical Laboratory, Santa Clara, Calif.), the disclosures of which are incorporated herein by reference in their entirety.
Thus, there is the need in the art for a simple and efficient method that permits the efficient rinsing of electronic component precursors, while at the same time providing an environmentally safe and economical method.